Fiber optic ribbons include optical waveguides such as optical fibers that transmit optical signals, for example, voice, video, and/or data information. Fiber optic cables using optical fiber ribbons can result in a relatively high optical fiber-density. Fiber optic ribbon configurations can be generally classified into two general categories. Namely, fiber optic ribbons with subunits and those without. A fiber optic ribbon with a subunit configuration, for example, includes at least one optical fiber surrounded by a discrete primary matrix, thereby forming a first subunit, and a second subunit having a similar construction with its own primary matrix. Then, the two subunits are connected and/or encapsulated by a secondary matrix, thereby forming a larger ribbon. On the other hand, fiber optic ribbons without subunits generally have a plurality of optical fibers surrounded by a single layer of matrix material.
Fiber optic ribbons are splicable using mass fusion techniques that can save the craftsman time when making optical connections. Nonetheless, the craftsman may have to splice less than every fiber in a ribbon and/or connect fibers from one ribbon to several different ribbons. Consequently, the craftsman may have to separate a ribbon into subsets or subgroups of fibers for connectorization. Optical fiber ribbons without subunits can present problems for the craft when attempting separation into subgroups of optical fibers. For example, when separating these optical fiber ribbons into optical fiber subsets, the craft may use expensive precision tools. Where the craft elects to separate the optical fiber ribbon into subsets by hand, or with a tool lacking adequate precision, stray optical fibers and/or damage to the optical fibers can result. Stray optical fibers can cause problems in optical ribbon connectorization, organization, stripping, and splicing. Additionally, damage to the optical fibers is undesirable and can render the optical fiber inoperable for its intended purpose.
There are fiber optic ribbon configurations that attempt to aid the separation of fiber optic ribbons into subsets without using subunits. For example, U.S. Pat. No. 5,982,968 requires an optical fiber ribbon of uniform thickness having V-shaped stress-concentrations in the matrix material that extend along the longitudinal axis of the fiber optic ribbon. V-shaped stress-concentrations can be located across from each other on the planar surfaces of the fiber optic ribbon, thereby aiding the separation of the fiber optic ribbon into subsets. However, the '968 patent requires a wider fiber optic ribbon because additional matrix material is required adjacent to the optical fibers near the V-shaped stress-concentrations to avoid stray optical fibers after separation. A wider ribbon requires more matrix material and decreases the optical fiber density.
Another example of a separable fiber optic ribbon is described in U.S. Pat. No. 5,970,196. More specifically, the '196 patent requires a pair of removable sections positioned in V-shaped notches located across from each other on opposite sides of the planar surfaces of an optical fiber ribbon. The removable sections are positioned between adjacent interior optical fibers of the optical fiber ribbon to facilitate the separation of the optical fiber ribbon into subsets at the V-shaped notches. The removable sections can either be flush with the planar surfaces of the optical fiber ribbon, or they may protrude therefrom. These known fiber optic ribbons have several disadvantages. For example, they can be more expensive and difficult to manufacture due to the required tooling and the like. Additionally; from an operability standpoint, the V-shaped stress-concentrations and/or V-shaped notches can undesirably affect the robustness of the optical fiber ribbon and/or induce microbending in the optical fibers.
Fiber optic ribbons that employ subunits to aid separation generally do not encounter these problems; however, they can have other problems. A conventional optical fiber ribbon 1 employing subunits encapsulated in a secondary matrix is shown in FIG. 1. Optical fiber ribbons having subunits can have several advantages, for example, improved separation, and avoidance of stray fiber occurrences. In particular, optical fiber ribbon 1 includes a pair of conventional subunits 2 having optical fibers 3 encapsulated in a primary matrix 5, which are then encapsulated in a secondary matrix 4. However, conventional optical fiber ribbon 1 has disadvantages. For example, one concern is the potential formation of wings W (FIG. 1) during hand separation of subunits 2. Wings W can be cause by, for example, a lack of sufficient adhesion between secondary matrix 4 and subunit matrix 5 and/or random fracturing of the secondary matrix during separation. The existence of wings W can negatively affect, for example, optical ribbon organization, connectorization, stripping, and/or splicing operations by the craft. Additionally, wings W can cause problems with ribbon identification markings, or compatibility of the subunit with ribbon handling tools, for example, thermal strippers, splice chucks, and fusion splicers.
Accordingly, the present invention is directed to fiber optic ribbon designs that substantially obviates one or more of the problems and disadvantages of the prior art. Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the apparatus and process particularly pointed out in the written description and claims, as well as the appended drawings.